Did you know that a type of bacteria can be used to help treat cancer? One in particular, called Bacillus Calmette-Guérin (BCG), is the most commonly used treatment for people with high-risk non-muscle-invasive bladder cancer (NMIBC). After surgery to remove visible tumors, BCG is often the first choice to help prevent the cancer from coming back or getting worse.

Bladder cancer begins in the lining of the bladder and is the sixth most common cancer in males worldwide, according to the World Health Organization (WHO).

When bladder cancer is found early, treatment is more likely to work well. For people with early-stage high-risk NMIBC — and in some intermediate-risk cases — BCG is considered the standard treatment. Before starting BCG therapy, most people undergo a procedure called transurethral resection of bladder tumor (TURBT) to remove tumors from the bladder lining.

In this article, we’ll cover how BCG is used to treat bladder cancer, when it’s most effective, common and long-term side effects, and how well it works over time.

What Is BCG, and How Is It Used in Bladder Cancer?

Bacillus Calmette-Guérin is a weakened form of the bacterium that causes tuberculosis (TB). It’s also used in vaccines to prevent TB. For cancer treatment, BCG is specially prepared so it can no longer cause illness.

In bladder cancer, BCG works by activating the immune system inside the bladder. It triggers immune cells to recognize and attack cancer cells growing in the bladder lining. This type of treatment is called immunotherapy: It helps the body’s immune system fight cancer.

The first phase of BCG treatment is called induction therapy. This usually involves weekly treatments for six weeks. After induction therapy, your doctor will check how well the treatment worked and decide whether more treatment is needed.

If needed, you may receive maintenance therapy — a second phase of treatment that helps keep the cancer from coming back. Maintenance therapy usually involves three weekly treatments every few months. Some people continue maintenance therapy for up to three years.

The goal of BCG therapy is to help prevent bladder cancer from growing or coming back.

Who Can Receive BCG Treatment for Bladder Cancer?

BCG treatment is used for certain types of early-stage bladder cancer. It’s especially recommended for people diagnosed with high-risk NMIBC.

“Non-muscle-invasive” means that the cancer has not spread into the bladder’s muscle layer — it remains in the inner lining of the bladder wall.

BCG isn’t effective for bladder cancer that has metastasized (spread) to the muscle layer or beyond the bladder to other parts of the body. That’s because BCG is placed directly into the bladder (through a thin tube called a catheter) and can’t reach cancer cells outside the bladder lining.

Before BCG treatment begins, a TURBT procedure is done to remove all visible cancer cells from the bladder.

For people with NMIBC, BCG is typically used when the cancer is considered high-risk, meaning there’s a higher chance the cancer could recur (return) or spread after treatment. In some cases, BCG may also be used for intermediate-risk NMIBC, especially if other treatments, like intravesical chemotherapy, aren’t working well or can’t be tolerated.

What Happens During BCG Treatment?

When used to treat bladder cancer, BCG is a type of intravesical therapy — meaning it’s placed directly into the bladder through the urethra (the hollow tube through which urine leaves the body).

Here’s how the treatment generally works:

1. Before your treatment, your doctor may ask you to stop drinking fluids for a few hours. This helps prevent a full bladder, which could dilute the medication and make it less effective.
2. Just before the procedure, your urine will be tested for signs of infection.
3. Your urethra will be numbed with a local anesthetic.
4. A catheter — a thin, flexible tube — will be gently inserted through the urethra into the bladder.
5. The BCG solution is then passed through the catheter into the bladder, and the catheter is removed.

Afterward, you'll be asked to hold your urine for about two hours. This gives the BCG enough time to coat the bladder walls and trigger an immune response.

When it's time to urinate, you’ll need to follow some safety steps to protect others and the environment from the BCG bacteria. We’ll cover those next.

What Precautions Should You Take After BCG Treatment?

After BCG treatment, your urine will contain the weakened bacteria used during therapy. While this bacteria doesn’t usually cause illness in healthy people, it can be harmful to others, especially those with weakened immune systems.

To protect others and prevent the bacteria from spreading, you’ll need to follow a few precautions for at least six hours after each treatment. These include:

• Avoiding using public toilets during this time
• Sitting down to urinate to reduce the risk of splashing
• Pouring household bleach into the toilet after you pee — Let it sit for about 15 minutes, and then flush. (Your healthcare provider can give you specific instructions.)
• Drinking plenty of fluids for the next 24 hours to help flush the BCG out of your bladder
• Avoiding sex for at least 24 hours after treatment — If you do have sex during your course of BCG therapy, use a condom every time to prevent exposing your partner to the bacteria.

What Are the Side Effects of BCG Treatment?

BCG treatment can cause short-term side effects shortly after each treatment. In fact, one recent study found that about 75 percent of people treated with BCG experience some temporary side effects.

• Blood in the urine
• Pain or burning when urinating
• Flu-like symptoms that last for 24 to 48 hours after treatment, including low fever (99-100 degrees Fahrenheit), fatigue, joint pain, and muscle aches
• A need to urinate more often or urgently

If you have frequent urination or any other side effects, tell your healthcare team. They may be able to help ease your discomfort.

Infection

Rarely, BCG can lead to more serious complications. In very uncommon cases, the bacteria used in BCG therapy can spread beyond the bladder and cause an infection in the body. This type of infection is similar to TB and can occur during treatment or even months later. It’s important to know the signs so you can get medical help right away.

Call your healthcare provider immediately if you experience any of the following:

• Skin rash
• High fever lasting more than 48 hours
• Chills
• Nausea or vomiting
• Joint or muscle pain
• Cough

Rare Side Effects

Other rare side effects of BCG treatment that have been reported include:

• Loss of bladder control
• Urinary retention (difficulty starting to pee)
• Urinary tract infections
• Bladder contracture (thickening or scarring of the bladder muscles), which may affect how much urine your bladder can hold

These more serious side effects are rare. One study found that only about 2 percent of people experienced side effects serious enough to require medication or hospitalization.

Your cancer care team will help you weigh these risks against the potential benefits of using BCG to treat your bladder cancer.

How Effective Is BCG Treatment?

BCG treatment is the first-line therapy for early-stage NMIBC. For people with NMIBC, receiving BCG after TURBT helps lower the risk of recurrence or progression (getting worse).

However, even with BCG treatment, bladder cancer will come back in about 40 percent of people.

The effectiveness of BCG can vary depending on several factors, including age and whether someone receives the full, recommended course of treatment. This is also true for other bladder cancer treatment options.

A 2024 study of more than 2,600 people with NMIBC found that those age 70 or younger had better overall survival, cancer-specific survival, and recurrence-free survival compared to those older than 70. However, there was no difference in how often the cancer progressed (got worse).

While age didn’t affect how often cancer progressed, the study found that older adults who completed the full course of BCG had similar progression outcomes as younger people. This suggests that finishing treatment may help prevent bladder cancer from getting worse, regardless of age.

These findings highlight that it’s important to make decisions about your bladder cancer treatment with your oncology team. Their expertise will help you decide together on the best treatment plan for your needs.

Talk With Others Who Understand

MyBladderCancerTeam is the social network for people with bladder cancer and their loved ones. On MyBladderCancerTeam, members come together to ask questions, give advice, and share their stories with others who understand life with bladder cancer.

Have you had BCG treatment for bladder cancer? What advice would you give people who are going to receive BCG therapy? Share your experiences in the comments below, or start a conversation by posting to your Activities page.